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Remote sensing of stratocumulus clouds: Uncertainties and biases due to inhomogeneity

Zinner, Tobias und Mayer, Bernhard (2006) Remote sensing of stratocumulus clouds: Uncertainties and biases due to inhomogeneity. Journal of Geophysical Research, 111, D14209. DOI: 10.1029/2005JD006955.

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Offizielle URL: http://www.agu.org/journals/jd/

Kurzfassung

Standard cloud remote sensing techniques rely on two basic assumptions: First, clouds are assumed to be plane-parallel and homogeneous within each satellite pixel. Second, pixels are assumed independent and the net horizontal radiative transport between pixels is neglected. These assumptions cause considerable uncertainty and bias in the retrieval of cloud properties, which depend on the sensors spatial resolution as well as the illumination and observation geometry. The errors are quantified for several typical sensor settings. Basis of the investigation is a high resolution three-dimensional cloud data set of marine stratocumulus obtained from airborne radiance observations. For this predefined cloud data the sensor signals are simulated using a 3D Monte Carlo radiative transfer model. Cloud properties (optical thickness, effective radius) are retrieved for the simulated observations using a two-channel retrieval, which are then compared to the given cloud data. For the retrieval of the optical thickness the main findings are: Large uncertainty of individual pixel values occurs for a high spatial resolution (e.g. airborne sensors) due to non-negligible horizontal photon transport at this pixel size. For the typical polar orbiting and geostationary sensor settings the neglect of sub-pixel inhomogeneity takes effect as well. Nonetheless, biases are generally small within +/-5%, if pixels are overcast. If this is not guaranteed, the bias grows rapidly -- e.g. to typical underestimations of 20% and more for a geostationary sensor. For the retrieval of effective radius values are generally found to be about 5% larger than expected for idealized homogeneous plane-parallel cloud conditions.

Dokumentart:Zeitschriftenbeitrag
Titel:Remote sensing of stratocumulus clouds: Uncertainties and biases due to inhomogeneity
Autoren:
AutorenInstitution oder E-Mail-Adresse der Autoren
Zinner, TobiasNICHT SPEZIFIZIERT
Mayer, BernhardNICHT SPEZIFIZIERT
Datum:11 Juli 2006
Erschienen in:Journal of Geophysical Research
Referierte Publikation:Ja
In Open Access:Nein
In SCOPUS:Ja
In ISI Web of Science:Ja
Band:111
DOI :10.1029/2005JD006955
Seitenbereich:D14209
Status:veröffentlicht
Stichwörter:remote sensing, inhomogeneity, clouds, 3D radiative transfer
HGF - Forschungsbereich:Verkehr und Weltraum (alt)
HGF - Programm:Weltraum (alt)
HGF - Programmthema:W EO - Erdbeobachtung
DLR - Schwerpunkt:Weltraum
DLR - Forschungsgebiet:W EO - Erdbeobachtung
DLR - Teilgebiet (Projekt, Vorhaben):W - Projekt Partikel und Zirren II (alt)
Standort: Oberpfaffenhofen
Institute & Einrichtungen:Institut für Physik der Atmosphäre > Fernerkundung der Atmosphäre
Hinterlegt von: Dr.rer.nat. Tobias Zinner
Hinterlegt am:20 Apr 2007
Letzte Änderung:11 Nov 2014 21:56

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